diff --git a/matsciml/datasets/transforms/pbc.py b/matsciml/datasets/transforms/pbc.py
index eedaacbf..a363ce91 100644
--- a/matsciml/datasets/transforms/pbc.py
+++ b/matsciml/datasets/transforms/pbc.py
@@ -187,9 +187,12 @@ def __call__(self, data: DataDict) -> DataDict:
             raise RuntimeError(f"Requested backend f{self.backend} not available.")
         data.update(graph_props)
         if not self.allow_self_loops:
-            mask = data["src_nodes"] == data["dst_nodes"]
+            # this looks for src and dst nodes that are the same, i.e. self-loops
+            loop_mask = data["src_nodes"] == data["dst_nodes"]
             # only mask out self-loops within the same image
-            mask &= data["unit_offsets"].sum(dim=-1) == 0
+            image_mask = data["images"].sum(dim=-1) == 0
+            # we negate the mask because we want to *exclude* what we've found
+            mask = ~torch.logical_and(loop_mask, image_mask)
             # apply mask to each of the tensors that depend on edges
             for key in ["src_nodes", "dst_nodes", "images", "unit_offsets", "offsets"]:
                 data[key] = data[key][mask]
diff --git a/matsciml/datasets/transforms/tests/test_pbc.py b/matsciml/datasets/transforms/tests/test_pbc.py
index 2878f614..90bbaa3e 100644
--- a/matsciml/datasets/transforms/tests/test_pbc.py
+++ b/matsciml/datasets/transforms/tests/test_pbc.py
@@ -56,9 +56,7 @@
 )
 @pytest.mark.parametrize("self_loops", [True, False])
 @pytest.mark.parametrize("backend", ["pymatgen", "ase"])
-@pytest.mark.parametrize(
-    "cutoff_radius", [6.0, 9.0, 15.0]
-)  # TODO figure out why pmg fails on 3
+@pytest.mark.parametrize("cutoff_radius", [6.0, 9.0, 15.0])
 def test_periodic_generation(
     coords: np.ndarray,
     cell: np.ndarray,
@@ -84,4 +82,31 @@ def test_periodic_generation(
     counts = Counter(src_nodes)
     for index, count in counts.items():
         if not self_loops:
-            assert count < 10, print(f"Node {index} has too many counts. {src_nodes}")
+            # TODO pymatgen backend fails this check at cutoff radius = 15
+            # and I don't know why
+            assert count <= 10, f"Node {index} has too many counts. {src_nodes}"
+
+
+def test_self_loop_condition():
+    """Tests for whether the self-loops exclusion is behaving as intended"""
+    coords = torch.FloatTensor(alumina.cart_coords)
+    cell = torch.FloatTensor(alumina.lattice.matrix)
+    num_atoms = coords.size(0)
+    atomic_numbers = torch.ones(num_atoms)
+    packed_data = {"pos": coords, "cell": cell, "atomic_numbers": atomic_numbers}
+    no_loop_transform = PeriodicPropertiesTransform(
+        cutoff_radius=6.0, backend="ase", allow_self_loops=False
+    )
+    no_loop_result = no_loop_transform(packed_data)
+    # since it's no self loops this sum should be zero
+    same_node = no_loop_result["src_nodes"] == no_loop_result["dst_nodes"]
+    same_image = no_loop_result["images"].sum(dim=-1) == 0
+    assert torch.sum(torch.logical_and(same_node, same_image)) == 0
+    allow_loop_transform = PeriodicPropertiesTransform(
+        cutoff_radius=6.0, backend="ase", allow_self_loops=True
+    )
+    loop_result = allow_loop_transform(packed_data)
+    # there should be some self-loops in this graph
+    same_node = loop_result["src_nodes"] == loop_result["dst_nodes"]
+    same_image = loop_result["images"].sum(dim=-1) == 0
+    assert torch.sum(torch.logical_and(same_node, same_image)) > 0